The United States on Friday congratulated Armenia and Azerbaijan on concluding negotiations on a historic peace treaty. The US described it as an opportunity for both nations to turn the page on a decades-old conflict,

Armenian and Azerbaijani officials said on Thursday that they had agreed the text of a peace agreement to end nearly four decades of conflict between the South Caucasus countries, a sudden breakthrough in a fitful and often bitter peace process.

But hurdles remain. Azerbaijan also said Armenia’s constitution must “eliminate the claims against the sovereignty and territorial integrity of Azerbaijan,” as a prerequisite to allow for the signing of the peace treaty.

Armenia and The Azerbaijan Republic have reached an agreement on a peace treaty, marking a significant step toward ending nearly four decades of conflict between the two former Soviet republics, officials from both countries announced on Thursday.

Armenia and Azerbaijan will not deploy third-country forces along their border after the two sides sign a peace agreement, Armenian Prime Minister Nikol Pashinyan said on Thursday. Officials in Yerevan and Baku said earlier they had agreed the text of a peace agreement to end more than three decades of conflict between their countries,

Armenia and Azerbaijan agreed to the terms of a long-awaited peace treaty Thursday that could end a decades-long conflict that began with the fall of the Soviet Union.

The two South Caucasus nations, former Soviet states, have fought multiple wars since the 1980s when Nagorno-Karabakh, an ethnically Armenian region broke away from Azerbaijan.

Armenia and Azerbaijan were locked in conflict over Nagorno-Karabakh for nearly four decades after the Soviet Union they were both members of collapsed.